You will need to do a quest and I recommend a higher set level and alot of stimpaks because you are going to need to fight ALOT of mirelurks. Travel to the "Rook Family House" on arrival you will see a man atop his house shooting off some mirelurks. Kill the remaining mirelurks and the man on his house will eventually allow around back the house where you will meet. Talk to "Barney Rook" with his quest of reactivating the turrets around town and at the end when you are prompted to return to Barney you will be told that Reba II is on the table in the back. Grab it and youre done (: All details will be posted below

Scoped Hunting rifle, 50% more damage to mirelurks and bugs (if high enough level possibility is will be a .50)

Heres the area you need to go to on the map, this shows where Salem is the house is right above salem. Its the very tip of that part of land, cant miss is.
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Here is a video for you if thats your thing